Wound dressings with layers for absorbing body fluids are known in the art. Absorbent layers are provided for the uptake of body fluids, especially wound exudate, so as to enable the wound dressing to keep a constant moist environment over the wound site, and at the same time avoiding maceration of the skin surrounding the wound.
Much effort has been directed to enhancing the rate of uptake and capacity of the wound dressing, in particular the absorbent layer, to uptake body fluids. Absorbent layers in wound dressings have comprised hydrocolloid, super absorbents, foams and synthetic materials which have extensive capacity to absorb body fluids, especially wound exudate.
However, increasing the capacity and rate of fluid uptake within a wound dressing may give rise to problems, both in assuring that the body fluids do not migrate from the wound dressing and in assuring the wound does not dry out.
Hydrocolloid dressings are some of the most efficient and mostly used dressings, being skin-friendly, absorbent and capable of creating moist wound healing conditions. However, when used on some exuding wounds, the absorption rate tends to be too low. The advantages of the hydrocolloid dressing is the ability of creating a moist wound healing environment and acting as a barrier against bacteria.
A frequent problem when treating exuding wounds is maceration. Usually the absorbent part of the dressing is optimised to substantially vertical absorption, so that the skin surrounding the wound is not exposed to the exudate in order to avoid maceration of this healthy, but fragile skin. However, these properties are limiting the absorption capacity of the dressing to the part of absorbent material being directly over the wound. Barrier cream/skin conditioning paste, such as zinc paste, may be used on the surrounding skin in order to avoid the maceration, but the paste will often inhibit both the adhesive tack of the dressing as well as the ability of absorbing exudate.
Highly exuding wounds are often treated with foams or alginate, which are capable of absorbing high amounts of exudate but requires additional cover dressings, as well as the risk of maceration is high. The retention of foam is low, which may be a problem when used on body parts being exposed to pressure.
A way of overcoming the problems with limited absorption capacity is to create a dressing with high permeability. This is usually done by using a backing layer being more permeable to vapour, but still liquid and bacteria impermeable. Using such a film the absorption capacity will rise when the permeability rises, enhancing the absorption capacity of the dressing. The capacity rises due to evaporation of moisture through the backing layer.
Various absorbent dressings are known:
From International Patent Application No. WO A 99/08724 is known a dressing comprising multiple layers. A wound contacting layer, being substantially free from adhesive and hydrocolloids, gelling and absorbing layers and a hydrophobic backing layer. The layers are joined by lamination, using pressure and heat.
U.S. Pat. No. 5,086,764 discloses a wound dressing with an adhesive base sheet at the skin facing side, on top of the base sheet an absorbent pad, the top surface of the pad having a hydrophobic backing. The base sheet has a central aperture over the wound site in order to allow quick uptake of wound exudate into the absorbent pad. On top of the absorbent pad may be a top film for fixation. It is possible to remove the top film and change the absorbent pad without detaching the base sheet from the skin. The hydrophobic backing of the absorbent pad provides a bacteria proof barrier. The reference is silent with respect to the vapour permeability of this barrier. The hydrophobic coating is preferably a fluorocarbon such as SCOTCHGARD, which has a low vapour permeability.
European Patent Application No. EP A1 641 553 discloses a securement for a wound dressing, in which an adhesive frame is mounted around the wound, an absorbent pad is placed over the wound and then a cover layer is placed on top. The cover layer is fixed detachably to the adhesive frame. Thus, the wound dressing is in the form of an assembly.
In International Patent Application No. WO 91/01706 is shown a wound dressing comprising a vapour permeable top film, over an absorbent foam pad, and an skin-contacting adhesive layer with an aperture over the wound. The top film is laminated to the foam pad.
European Patent Application No. EP A1 236 104 discloses a wound dressing with an adhesive foam frame on top of which a film and an absorbent pad is fixed.
International Patent Application No. WO A 98/31402 discloses a wound dressing comprising a perforated wound contacting layer such as a film or a net, a backing layer, and between these two layers is a fibrous absorbent layer. The absorber and the backing layer are combined by heat-lamination.
International Patent Application No. WO A 97/07759 discloses a wound dressing comprising a backing layer partly being coated with adhesive. The adhesive coating is in the form of a pattern in which the percentage of adhesive in the marginal region is higher than in the central region. The dressing may further comprise an absorbent material in the form of a hydrogel or alginate.
When using highly permeable films in dressings the different parts of the dressing are combined, usually by coating the backing, fully or partly, with adhesive, in order to keep the dressing together. The adhesive coating will however, decrease the permeability of the film significantly. Another way of producing such a dressing is to combine the layers of the dressing by lamination. However, the heat and pressure of the lamination process may change the permeability properties of the backing layer, as well as the structure of the absorbent layer may be crushed.
The flexibility of a dressing wherein the layers are tied together by adhesive or lamination may also be reduced, enhancing the risk of handling problems and leakage when used on curved body parts.
Thus, there is still a need for a flexible, highly absorbent wound dressing being capable of absorbing large amounts of wound exudate without giving rise to maceration.